leaded or super unleaded?

[gotoneagain]

saw it on a past thread that if car is not mapped top run super unleaded then theres not much point putting it in over normal 95ron unleaded as theres no knock sensor to adjust timing to take full benefit of super 98ron unleaded? any thoughts on this as i cant help filling with super!!

[maxfield]

Stick with 95 and save yourself money.

[tezk]

you'll get no advantage what so over as the timing on e30's doesn't take into account fuel octane rating. But then its your money and if you happy spending the extra (and getting no benefit) then feel free!

[zimmerbimmer1]

I must admit in my E34 535i I have run it on super unleaded and after the second tankful in a row
the car feels so much more responsive to the throttle pedal and it surprisingly knocks 0.5 of the 0-60 time

[Simon13]

rubbish super won't make a difference on a 3.5 M30 boat anchor. The only gain is it will give the pistons a little clean

[bss325i]

Higher octane will help. All e30 engines were designed to run on leaded 4 star which is 98 ron. My sport runs noticabley better on super. If you ran a car up on the rollers with the two different grades of fuel, you would get different power readings all be it a small difference.

[munky30]

I thought they were designed and mapped to run on 91 ron...

[snoops]

Higher octane will help. All e30 engines were designed to run on leaded 4 star which is 98 ron. My sport runs noticabley better on super. If you ran a car up on the rollers with the two different grades of fuel, you would get different power readings all be it a small difference.

I thought 98 as well

[bss325i]

I thought they were designed and mapped to run on 91 ron...

Thats the minimum ratted fuel they can run on, manufacture's have to allow for the different grades of fuel avail but for optimum performance they should be run on 98 ron, i think it even says in the hand book about being able to run on a min of 91 ron but not at optimum power.

[Simon13]

yes but the engine managment has no way of recognising higher octane fuel so it can't benefit from it fully at all. So it's down to compression ratios i guess

Alpina B6's with the 3.5's had a switch so you could run them on low octane and high octane fuel so you couldn't damage the lump on sh!te fuel. So the Ecu had 2 sets of maps for each fuel as such. Normal E30's don't even have this

[munky30]

I thought they were designed and mapped to run on 91 ron...

Thats the minimum ratted fuel they can run on, manufacture's have to allow for the different grades of fuel avail but for optimum performance they should be run on 98 ron, i think it even says in the hand book about being able to run on a min of 91 ron but not at optimum power.

fair enough. I just remember someone saying it on here... this subject seems to come up a lot!

[bss325i]

yes but the engine managment has no way of recognising higher octane fuel so it can't benefit from it fully at all. So it's down to compression ratios i guess

Alpina B6's with the 3.5's had a switch so you could run them on low octane and high octane fuel so you couldn't damage the lump on sh!te fuel. So the Ecu had 2 sets of maps for each fuel as such. Normal E30's don't even have this

Yes i understand, the motronic system has no knock sensor or oxygen sensor to register afr's but it is originaly mapped to run on 98 ron but 91 is the min it can safely run on the original map, it just wont make optimum power.

[bss325i]

Just checked the handbook and a haynes manual and they both say 98 ron. The hand book also says min of 91 ron.

[daimlerman]

When Miller modified my 2.7 chip I asked about this,they claim to have set it to suit super.The car does pull better on super,but there again when I cannot get to the super pump I stick a tankful of the standard stuff in and I do not get any pinking.Seems to be more efficent on super,I get about 1mpg more over the tankful.As has been said,you pays your money and makes your choice...

[gotoneagain]

seems like this has sparked a bit of conflicting theories, book does say for pre facelift 325i s 98ron but on the inside of my filler cap it says tuned for unleaded 95ron!! only thing i can say is if i put super in my sooty van 1000cc i must admit i cant really tell much only that it runs slightly cooler because of the quicker/easier burn, also i have tried pro boost made by silkolene and again not much to report, its supposed to be a fuel conditioner, are we really getting shit fuel at the pumps?!!! that we have to add allsorts of "products" to it...

[Brianmoooore]

This come up again!! The RON of petrol has nothing to do with how much power it produces!
105 RON petrol doesn't in itself produce the slightest bit more power than 91 RON. What 105 RON petrol does do is allow you to use different settings on the engine (timing, compression, etc.) to produce more power.
E30 engines have no feedback system to recognise what grade of fuel is used, therefore no increase in power.
All E30 engines require is the minimum RON rating to prevent pinking.

[leslie]

Is there an avantage in using this fuel in so far as (BP Ultimate claim) it cleans up, and keeps clean, valves and injectors and gives better mpg (BP claim average 13 miles more per tank) they also claim it gives less emissions. or is this just b******s as well?

[jokipea]

The alleged better mpg gained from using higher octane petrol isn't enough to justify paying so much more for it.

[march109]

This come up again!! The RON of petrol has nothing to do with how much power it produces!
105 RON petrol doesn't in itself produce the slightest bit more power than 91 RON. What 105 RON petrol does do is allow you to use different settings on the engine (timing, compression, etc.) to produce more power.
E30 engines have no feedback system to recognise what grade of fuel is used, therefore no increase in power.
All E30 engines require is the minimum RON rating to prevent pinking.

Brian is 100% right as per usual, maybe some of you should Google the term RON, RON is the reaserch octane rating and refers to how much ENERGY is required to ignite that particular fuel, it still emits the same energy per litre wether its 91RON or 98RON or 102RON

The higher the RON the better suited the fuel is to high temp or stress or pressure engines, such as diesels which run hotter (mainly because its harder to ignite diesel), or turbo'd cars where the fuel could ignite early (detonation) under the extra pressure.

No engine will ever make use of the extra RON if it doesn't have knock sensor, end of story.

However the 'premium' fuels have added detergents which will benefit some engines, however for some older engines I suspect the carbon build up actually helps them as it acts as a sealent so only use these if your engine is 100% tickety boo.

BTW they use the same detergents in these fuels as they use in fuel additives that you see in Halfords and this is a much cheaper way of getting your fix if this is what you demand to waste your money on!

[ShakeyC]

These new super fuels have more cleaning properties so cleaning up a manky old engine would help it regain some lost performance in that respect bit like redex. Also the fuel ment to atomise better to geta more efficient burn resulting in lower emmissions and over so slightly more poke.

Then again i have no idea what im on about

[Morat]

Mainly useful for Jap imports which require it. Otherwise don't bother. Spend the money you save on better tyres.

[M3Tony]

And for E30 M3 (1990) - still no benefit in running 98 fuel rather than 95 ? Wife just spotted my last refill bill at £65+ !!

[harry_p]

95 is probably fine for pottering around town or gentle motorway work, however mine has a 98ron only sticker inside the petrol flap, so that's what i use 99.9% of the time.

only time i will choose a 95 is if i miss time my fuel stops and have to use a ripoff motorway service station

[munky30]

98 Rons. (-97 rons = 1 ron )




edited by billgates as it was messing up the page structure

Billgates is mean and has no sense of humour.

[Gwynleym10]

http://driving.timesonline.co.uk/tol/li ... 025403.ece

^ this is an interesting article on the subject.

It comes to the conclusion that super unleaded can be good for engines - but its purely down to their cleaning properties. If you think of washing up liquid, tescos value does the job, but fairy does it a bit better. It is the same with the detergents in super unleaded.

Our engines have a few years old now, and probably a bit gummed up - so a tank or two of super probably will make them perform better. Probably not worth doing it all the time though.

I try and do every 9 and 10 tanks of super and 12345678 normal.

[march109]

Didn't read the article, but I believe thats what I said.

However Redex is a cheaper way of doing this, and beware if carbon deposits are sealing your engine from leaking/mixing oil fuel or air where it shouldn't go this will do more harm than good!

good luck.